The present invention relates to a substrate detecting device for detecting both presence and off-position (positional deviation) of a substrate, such as a semiconductor wafer and also relates to a method of detecting the presence and off-position of the substrate.
Generally, in order to perform a designated process for the substrate, for example, the semiconductor wafer in a processing apparatus devices, it is executed to first take out one substrate from a cassette unit capable of accommodating a plurality of substrates and secondly load the substrate into a load-locking chamber capable of forming a vacuum in its interior. After evacuating the interior of the load-locking chamber, the substrate is loaded into the processing apparatus via a vacuum transfer chamber evacuated in advance. When unloading the processed substrate out of the processing apparatus, it is transferred in the opposite course to the above-mentioned course.
The reason for the load-locking chamber""s mediation in loading and unloading the substrate is as follows: for the purpose of delivering the substrate between the cassette unit exposed into the atmospheric pressure and the vacuum transfer chamber or the processing apparatus maintained in the vacuum, if there is such a load-locking chamber, which is capable of getting both vacuum condition and atmospheric condition rapidly and easily, between the cassette unit and the vacuum chamber or the processing apparatus, the speedy operation of loading/unloading of the wafers could be accomplished without breaking a vacuum in the vacuum transfer chamber or the processing apparatus.
Besides, by the above-mentioned reason, the volume of the load-locking chamber is established as small as possible. Further, the load-locking chamber is provided, at its loading/unloading port for the substrate, with a gate valve which allows the port to be closed in an airtight manner. However, if the substrate is accommodated in the load-locking chamber while being shifted from the formal position in excess of the allowance, it may be an impossibility for a transfer arm to carry the substrate in the off-position. Alternatively, if the worst comes to the worst, the substrate in the off-position may be pinched and broken by the gate valve.
In order to solve such a drawback, there has been proposed a substrate detecting device which is arranged in the load-locking chamber, for confirming the presence of the substrate in the chamber and the existence of the substrate""s off-position in excess of a predetermined allowance for the substrate.
FIG. 14 is a plan view showing the above load-locking chamber and the substrate detecting device disposed in the load-locking chamber and FIG. 15 is a perspective view showing the interior of the load-locking chamber. The load-locking chamber 2 is constituted by a thin and square container capable of forming a vacuum, which is made of e.g. stainless steel. The load-locking chamber 2 is provided, on opposing walls thereof, with loading/unloading ports 4, 6 through which the substrate W, such as semiconductor wafer, is carried in and out. Gate valves G1, G2 capable of closing in an airtight manner are arranged on the loading/unloading ports 4, 6, respectively.
In the load-locking chamber 2, for example, three support pins 8 movable up and down are arranged so as to stand in the form of a substantially regular triangle and support the substrate W thereon. In a position corresponding to the general center of the substrate W, an optical emitter 9 and an optical receptor 10 in pairs are respectively arranged below and above the substrate W, for identifying the existance of the substrate. Also in a position separated outward from the outer peripheral edge of the substrate W by a small clearance L1, a lower optical emitter 11 and an upper optical receptor 12 in pairs are arranged in order to confirm whether the substrate is in the xe2x80x9coff-positionxe2x80x9d or not. In the shown example, three pairs of emitters 11 and receptors 12 for confirmation of the off-position are arranged in the circumferential direction of the substrate W at substantially regular intervals. With the arrangement, when the substrate W is shifted from the formal position in excess of an allowance (L1), the confirmation of the off-position is carried out since the light from the emitter 11 existing in the direction of the off-position is cut off by the substrate W.
Meanwhile, in the conventional substrate detecting device mentioned above, the rising in manufacturing cost is caused due to the requirement for at least four pairs of emitters and receptors. Additionally, with the arrangement where the emitters 11 and the receptors 12 for confirmation of the off-position are positioned outside the outer peripheral edge of the substrate, the interior space or volume of the load-locking chamber 2 is increased to cause the installation space to be enlarged with an increase in time required for evacuating the chamber.
Under such a situation, the present invention originates in the demand for solving the above-mentioned problems effectively. It is therefore an object of the present invention to provide a substrate detecting device which is capable of detecting the presence of the substrate and the existence of the substrate""s off-position by the information from a small number of substrate detecting sensing parts and also provide a substrate detecting method using the above substrate detecting device.
The 1st. feature of the present invention resides in: a substrate detecting device for detecting presence and off-position of a substrate mounted on a substrate mounting part, the substrate detecting device comprising a plurality of substrate sensing parts each of which is arranged in a position inward departing from an outer peripheral edge of the substrate arranged in a designated position on the substrate mounting part, by a predetermined distance and which are arranged in the circumferential direction of the substrate at intervals; and a judgement controlling unit for judging the presence of the substrate on the substrate mounting part and the existence of the substrate""s off-position being deviated from the designated position, on the ground of respective outputs from the substrate sensing parts.
With the above constitution, since the plural substrate sensing parts are arranged in respective positions just inward departing from the outer peripheral edge of the substrate and also departing from each other in the circumferential direction of the substrate, the judgement controlling unit can judge the presence of the substrate on the substrate mounting part and the existence of the substrate""s off-position in excess of an allowance predetermined for the substrate, on the basis of the outputs from the substrate sensing parts.
The 2nd. feature of the present invention resides in that the judgement controlling unit of the substrate detecting device judges the presence of the substrate on condition that at least one of the plural substrate sensing parts detects the presence of the substrate; and the off-position of the substrate on condition that at least one of the plural substrate sensing parts does detect the presence of the substrate and at least one of the other substrate sensing parts does not detect the substrate. In this case, it means that the substrate is in the off-position where it is shifted from the substantial center of the substrate toward the sensing part detecting the presence of the substrate.
The 3rd. feature of the present invention resides in that the substrate to be subjected to judgement for the presence and off-position is shaped to be substantially circular.
The 4th. feature of the present invention resides in that the substrate sensing parts are at least three in number. In this way, if only providing the sensing parts of three in number, more or less, then it is possible to confirm the presence of the substrate and the existence of off-position of the substrate, thereby not only reducing the number of sensors but controlling the installation space.
The 5th. feature of the present invention resides in that the plural substrate sensing parts are arranged in the circumferential direction of the substrate at substantially regular intervals.
The 6th. feature of the present invention resides in that the substrate detecting device further comprises a pair of opposing substrate restricting walls which are arranged on both sides of the substrate mounting part, for restricting the position of the substrate on the inside of the substrate restricting walls.
The 7th. feature of the present invention resides in that the substrate sensing parts of two in number, are arranged in a direction substantially perpendicular to the opposing direction of the substrate restricting walls in pairs.
The 8th. feature of the present invention resides in that the substrate to be subjected to judgments for the presence and off-position thereof is shaped to be substantially square.
The 9th. feature of the present invention resides in that the plural substrate sensing parts are arranged on respective corners of the square-shaped substrate.
The 10th. feature of the present invention resides in that the plural substrate sensing parts are arranged on two corners of respective corners of the square-shaped substrate, the two corners being in a diagonal direction of the substrate.
The 11th. feature of the present invention resides in that the substrate detecting device further comprises a pair of opposing substrate restricting walls which are arranged on both sides of the substrate mounting part, for restricting the position of the substrate to the inside of the substrate restricting walls, wherein a distance between the pair of opposing substrate restricting walls is longer than a distance between opposing sides defining the square-shaped substrate by a predetermined distance.
The 12th. feature of the present invention resides in that the plural substrate sensing parts of two in number are arranged in a direction substantially perpendicular to the opposing direction of the substrate restricting walls.
The 13th. feature of the present invention resides in that the substrate detecting device further comprises an accommodating chamber for accommodating the substrate mounting part therein, wherein the accommodating chamber is provided with an opening and closing door through which the substrate to be mounted on the substrate mounting part can be loaded into and unloaded from the accommodating chamber. control unit prohibits the closing operation of the opening and closing door when the off-position of the substrate is detected. Consequently, it is possible to prevent the substrate from being damaged by the door""s pinching.
The 15th. feature of the present invention resides in that the accommodating chamber is identical to a load-locking chamber capable of forming a vacuum therein.
The 16th. feature of the present invention resides in that the predetermined distance between the outer peripheral edge of the substrate and each of the substrate sensing parts ranges from 5 mm to 10 mm for the substrate of 12 inches in size.
The 17th. feature of the present invention resides in a method of detecting presence and off-position of a substrate mounted on a substrate mounting part by using a substrate detecting device, the substrate detecting device including the substrate mounting part for mounting the substrate thereon and a plurality of substrate sensing parts arranged in respective positions just inward departing from an outer peripheral edge of the substrate in a designated position on the substrate mounting part and also departing from each other in the circumferential direction of the substrate, the method comprising the steps of judging the presence of the substrate on condition that at least one of the plural substrate sensing parts does detect the presence of the substrate; and judging the off-position of the substrate on condition that at least one of the plural substrate sensing parts does detect the presence of the substrate and at least one of the other substrate sensing parts does not detect the substrate.